JPH0643386A - Temperature compensating structure for light source part or light receiving part - Google Patents

Abstract

PURPOSE:To prevent the optical characteristics of a light source part or a light receiving part from being degraded by temperature changed by equalizing a linear expansion coefficient for a member to hold a light emitting means or a photoelectric converting means and a member to hold an optical member. CONSTITUTION:A semiconductor laser 1 is fitted to a holding member 3, and the holding member 3 is fixed after the position is adjusted to a holding member 7. Further, a holding member 8 is fitted and fixed inside a holding member 7 so that the central axis can be coincident with an optical axis direction. On the other hand, a collimator lens 2 is fitted to a holding member 5 and fixed by a presser ring 6. Then, the holding members 5 and 8 are arranged so that the flange parts can be faced each other, and fixed with plural supports 9 between. In this case, the supports 9 are produced with low expansion materials, the length of the supports 9 is decided so as to compensate a distance between the semiconductor laser 1 and the collimator lens 2 corresponding to temperature changes, and the linear expansion coefficient is made equal for the holding members 3, 7 and 8 of the semiconductor laser 1 and the holding member 5 of the collimator lens 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensation structure such as an optical head used in an apparatus for recording information on an optical disc or reproducing information recorded on the optical disc, and more particularly to temperature compensation of collimation in a light source section. The present invention relates to a suitable temperature compensation structure.

[0002]

2. Description of the Related Art A conventional temperature compensation structure for a light source will be described with reference to FIG. In FIG. 3, the semiconductor laser 1 is
It is fitted to the holding member 23 and is fixed by the pressing ring 24. On the other hand, the collimator lens 2 that transforms the light emitted from the semiconductor laser 1 into a parallel light flux is fitted into a holding member 25 having a flange portion that projects outward at the lower end, and is fixed by a holding ring 26.

The holding member 23 is fastened by screws (not shown) between the surfaces perpendicular to the optical axis so that the position of the holding member 23 in the direction perpendicular to the optical axis can be adjusted.
Further, the holding member 28 has a cylindrical shape having a flange portion projecting inward at the upper end, and has a central axis inside the holding member 27 so that the position in the optical axis direction can be adjusted with respect to the holding member 27. It is fitted so that the optical axis directions thereof coincide with each other, and is fixed to the holding member 27 by a fixing means (not shown).

The holding member 25 and the holding member 28 are
The collar portions are arranged so as to face each other, and a plurality of (two in FIG. 3) supports 29 are sandwiched therebetween and fixed by screws 30. The spring washer 31 is interposed between the head of the screw 30 and the holding member 25 in order to loosen the screw 30. The light source unit having the above structure is provided in the device main body 3
The holding member 27 is supported by being fastened to the No. 2 by a screw (not shown).

Next, the temperature compensation of the light source section shown in FIG. 3 will be described with reference to FIG. As shown in FIG. 4, a heat sink 1a having a length of 2.45 mm is provided inside the semiconductor laser 1, and the material thereof is iron (Fe) at a portion having a length L ₁ = 0.85 mm and has a length of The portion of L ₂ = 1.6 mm is molybdenum (Mo). The semiconductor chip 1b is arranged at the tip of the heat sink 1a. Here, the linear expansion coefficient α _Fe of _iron is about 12 × 10 ⁻⁶ / ° C., and the linear expansion coefficient α _Mo of _molybdenum is about 5.4 × 10 ⁻⁶ / ° C. Therefore, the temperature characteristics of the heat sink 1a of the semiconductor laser 1 (= unit temperature (1 ° C.) dimensional change per change) ^{is, 1.6mm × 5.4 × 10 -6 /℃+0.85mm×12×10} -6 / C = 1.884 × 10 ⁻⁵ mm / ° C. (1)

The collimator lens 2 is an aspherical glass lens. The temperature characteristic of the working distance of the collimator lens 2 is 1.5 × 10 ⁻⁴ mm / ° C. Further, the wavelength characteristic of the working distance of the collimator lens 2 (= unit wavelength (1 nm)
Dimensional change per change) is 1.4 × 10 ^-4 mm / nm
The temperature characteristic of the wavelength of the emitted beam of the semiconductor laser 1 is 0.20 nm / ° C. Therefore, the temperature characteristic of the working distance of the collimator lens 2 is 1.5 × 10 ⁻⁴ mm / ° C. + 1.4 × 10 ⁻⁴ mm / nm × ^{0.1 when} the temperature characteristic of the wavelength of the semiconductor laser 1 is included. 20 nm / ° C. = 1.78 × 10 ⁻⁴ mm / ° C. (2)

The holding member 23 and the holding member 27, and the holding member 27 and the holding member 28 are in a fastening state with each other after the position adjustment. These holding members 23, 27, 28 are made of the same aluminum alloy (Al alloy). In the following description, the holding members 23, 27, 28 are collectively referred to as the first holding member. Mounting reference surface 1c of the semiconductor laser 1,
The distance between the support 29 and the mounting reference surface 29a between the holding member 28 and L ₃ is 8.83 mm, and the linear expansion coefficient of the aluminum alloy is 24 × 10 ⁻⁶ / ° C. Therefore, the temperature characteristic of the first holding member between the reference surface 1c and the reference surface 29a is 8.83 mm × 24 × 10 ⁻⁶ / ° C. = 2.1192 × 10 ⁻⁴ mm / ° C. (3) .

Similarly, the holding member 25 (in the following description,
(Referred to as a second holding member) and the support 29, the distance between the mounting reference surface 29b of the support 29 and the mounting reference surface 2a of the collimator lens 2 (L ₄ = 0.5 mm) shows that the second holding member has a temperature characteristic. SUS304 (coefficient of linear expansion = 17.2 x 10 ^-6 / ° C)
Therefore, 0.5 mm × 17.2 × 10 ⁻⁶ / ° C. = 8.6 × 10 ⁻⁶ mm / ° C. (4)

The support 29 has a length L ₅ = 1 mm and is made of a low expansion material (LEX15). LEX
The linear expansion coefficient of 15 is 1.4 × 10 ⁻⁶ / ° C. Therefore, the temperature characteristic of the length of the support 29 is 1 mm × 1.4 × 10 ⁻⁶ / ° C. = 1.4 × 10 ⁻⁶ mm / ° C. (5) In the figure, L ₆ = 0.83 mm, L ₇ = 4.55
mm.

By the way, the expansion of the heat sink 1a of the semiconductor laser 1, the second holding member 25, and the support 29 is caused by the collimator lens 2 and the chip 1 of the semiconductor laser 1.
It is a direction to bring b closer. On the other hand, the expansion of the first holding members 23, 27, 28 is a direction in which they are moved away from each other, and the directions in which the force acts due to the expansion are different. When the temperature characteristic between the collimator lens 2 and the chip 1b of the semiconductor laser 1 is obtained by taking such directionality into consideration, the following equation (3) -equation (1) -equation (4) -equation (5) = It becomes 1.8308 × 10 ⁻⁴ / ° C. (6).

Now, comparing equations (2) and (6), the values are almost equal. That is, the temperature characteristic of the working distance of the collimator lens 2 and the temperature characteristic of the distance between the collimator lens 2 and the chip 1b of the semiconductor laser 1 are substantially equal. Therefore, even if the working distance of the collimator lens changes due to temperature change, the collimator lens 2
The distance between the semiconductor laser 1 and the chip 1b of the semiconductor laser 1 changes by an amount substantially equal to the change of the working distance, and the collimation deviation is compensated.

[0012]

However, such a conventional temperature compensation structure has the following problems. 5A and 5B are diagrams schematically showing the holding member 25, the support 29, and the holding member 28 in FIG. 4. FIG. 5A shows a normal temperature state during adjustment, and FIG. 5B shows a high temperature state. There is. As described above, since the holding member 25 and the holding member 28 have different linear expansion coefficients, the mounting position of the support 29 is orthogonal to the optical axis between the holding member 25 and the holding member 28 at high temperature as shown in the figure. It shifts in the direction. That is, in the flange portions of the holding members 25 and 28, the holding member 28 having a larger coefficient of linear expansion has a longer protruding length of the flange portion, and the mounting position of the support of the holding member 28 is relatively outward, and the holding member 25 is relatively fixed. The support mounting position of is displaced inward. Such a shift also occurs at low temperatures. Due to this deviation, the positional relationship between the holding member 25 and the holding member 28, that is, the positional relationship between the semiconductor laser 1 and the collimator lens 2 may be destroyed due to the temperature change.

As described above, in the conventional temperature compensating structure, there is a problem in that the positional relationship in the optical axis direction is temperature-compensated, but the deviation tends to occur in the direction perpendicular to the optical axis. The present invention has been made in view of this point, the mounting position of the support interposed in the fastening portion of the holding member does not shift in the direction perpendicular to the optical axis, and the light emitting member or An object is to provide a temperature compensation structure in which the positional relationship between the photoelectric conversion means and the optical member is not broken.

[0014]

According to a first aspect of the present invention, there is provided a temperature compensating structure comprising: a first holding member for holding a light emitting means or a photoelectric conversion means; and a light beam emitted from the light emitting means or a light beam incident on the light receiving means. A second holding member for holding the optical member arranged in the optical path, and a support member having a linear expansion coefficient different from that of the first holding member, wherein the first and second holding members are the support. Fastened with a member sandwiched therebetween, the length of the support member in the fastening direction is determined so as to compensate for a change in the distance between the light emitting unit or the photoelectric conversion unit and the optical member against a temperature change, and In order to achieve the above object, the first and second holding members are configured to have equal linear expansion coefficients.

In the temperature compensating mechanism of the second aspect, at least one of the first and second holding members is composed of a plurality of members having the same linear expansion coefficient. The light emitting means in the temperature compensation structure according to claim 3 is a semiconductor laser. The photoelectric conversion means in the temperature compensation structure according to claim 4 is a PIN photodiode.

[0016]

In the present invention, since the first holding member and the second holding member have the same linear expansion coefficient, the expansion and contraction of the fastening portion are the same when the temperature changes, and the first holding member and the second holding member have the same expansion coefficient.
The mounting position of the support member interposed between the holding members does not shift between the holding members in the direction perpendicular to the optical axis. Therefore, even if there is a temperature change, the positional relationship between the first holding member and the second holding member, that is, the positional relationship between the light emitting means or the light receiving means and the optical member such as the collimator lens is not broken.

[0017]

1 is a sectional view for explaining a temperature compensation structure according to an embodiment of the present invention, showing a light source portion of an optical head. In FIG. 1, the semiconductor laser 1 includes a holding member 3
And is fixed by the pressing ring 4. On the other hand, the collimator lens 2 for making the light emitted from the semiconductor laser 1 into a parallel light flux is fitted to a holding member 5 having a flange portion protruding to the outside at the lower end portion and fixed by a holding ring 6.

The holding member 3 is fastened by screws (not shown) on the surfaces perpendicular to the optical axis so that the position of the holding member 3 in the direction perpendicular to the optical axis direction can be adjusted.
In addition, the holding member 8 has a cylindrical shape having a flange portion that protrudes inward at the upper end, and has a central axis inside the holding member 7 so that the position in the optical axis direction with respect to the holding member 7 can be adjusted. They are fitted so that the optical axis directions thereof coincide with each other, and are fixed to the holding member 7 by fixing means (not shown).

The holding member 5 and the holding member 8 are arranged such that the collar portions are opposed to each other, and a plurality of (two in FIG. 1) supports 9 are sandwiched therebetween and fixed by screws 10. ing. The spring washer 11 is interposed between the head of the screw 10 and the holding member 5 in order to loosen the screw 10. The light source unit having the above-described structure is supported by fastening the holding member 7 to the device body 12 with screws (not shown).

Next, the temperature compensation of the light source section shown in FIG. 1 will be described with reference to FIG. As shown in FIG. 2, a heat sink 1 having a length of 2.45 mm is provided inside the semiconductor laser 1.
There is a, and the material thereof is iron (Fe) in a portion having a length L ₁ = 0.85 mm and molybdenum (Mo) in a portion having a length L ₂ = 1.6 mm. The semiconductor chip 1b is arranged at the tip of the heat sink 1a. Here, the linear expansion coefficient α _Fe of _iron is about 12 × 10 ⁻⁶ / ° C., and the linear expansion coefficient α _Mo of _molybdenum is about 5.4 × 10 ⁻⁶ / ° C. Therefore,
The semiconductor temperature characteristics of the laser 1 of the heat sink 1a (= unit temperature (1 ° C.) dimensional change per change) ^{is, 1.6mm × 5.4 × 10 -6 /℃+0.85mm×12×10} -6 / ℃ = 1.884 × 10 ⁻⁵ mm / ° C. (11)

The collimator lens 2 is an aspherical glass lens. The temperature characteristic of the working distance of the collimator lens 2 is 1.5 × 10 ⁻⁴ mm / ° C. Further, the wavelength characteristic of the working distance of the collimator lens 2 (= unit wavelength (1 nm)
Dimensional change per change) is 1.4 × 10 ^-4 mm / nm
The temperature characteristic of the wavelength of the emitted beam of the semiconductor laser 1 is 0.20 nm / ° C. Therefore, the temperature characteristic of the working distance of the collimator lens 2 is 1.5 × 10 ⁻⁴ mm / ° C. + 1.4 × 10 ⁻⁴ mm / nm × ^{0.1 when} the temperature characteristic of the wavelength of the semiconductor laser 1 is included. 20 nm / ° C. = 1.78 × 10 ⁻⁴ mm / ° C. (12)

Holding member 3, holding member 7, and holding member 7
After the positional relationship is adjusted, the holding member 8 and the holding member 8 are in a fastening state with each other. In addition, the holding members 3, 7, and 8 are the same SUS30.
Made of 4 stainless steel. In this embodiment,
These holding members 3, 7 and 8 form a first holding member. Mounting reference surface 1c of semiconductor laser 1 and support 9
The distance L ₃ between the mounting reference surface 9a and the holding member 8 is 12.
It is 3 mm. The coefficient of linear expansion of SUS304 is 17.2.
× 10 ⁻⁶ / ° C. Therefore, the temperature characteristic of the distance between the reference surface 1c and the reference surface 9a of the first holding member is 12.3 mm × 17.2 × 10 ⁻⁶ / ° C. = 2.1156 × 10 ⁻⁴ mm / ° C. (13) ).

Similarly, the holding member 5 (second part of the present invention)
(Which constitutes the holding member of) and the mounting reference surface 9 of the support 9
b and the mounting reference surface 2a of the collimator lens 2 (L
₄ = 0.5 mm), the second holding member has the first
Since it is made of SUS304, which is the same as the holding member of No. 3, 0.5 mm × 17.2 × 10 ⁻⁶ / ° C. = 8.6 × 10 ⁻⁶ mm / ° C. (14)

The support 9 has a length L ₅ of 4.47 mm and is made of a low expansion material (LEX15). L
The coefficient of linear expansion of EX15 is 1.4 × 10 ⁻⁶ / ° C. Therefore, the temperature characteristic of the length of the support 9 is 4.47 mm × 1.4 × 10 ⁻⁶ / ° C. = 6.258 × 10 ⁻⁶ mm / ° C. (15) In the figure, L ₆ = 0.83 mm, L ₇ = 4.55
mm.

By the way, the expansion of the heat sink 1a of the semiconductor laser 1, the second holding member, and the support 9 is
This is a direction in which the collimator lens 2 and the chip 1b of the semiconductor laser 1 are brought close to each other. On the other hand, the expansion of the first holding member is a direction in which the collimator lens 2 and the chip 1b of the semiconductor laser 1 are moved away from each other, and the directions of the forces acting at the time of expansion are different. When the temperature characteristic of the distance between the collimator lens 2 and the chip 1b of the semiconductor laser 1 is calculated in consideration of such directionality, the formula (13) -formula (11) -formula (14) -formula (15) = 1.77862 × 10 ⁻⁴ mm / ° C. (16)

Here, comparing equations (12) and (16), the values are almost equal. That is, the temperature characteristic of the working distance of the collimator lens 2 and the temperature characteristic of the distance between the collimator lens 2 and the chip 1b of the semiconductor laser 1 are substantially equal. Therefore, even if the working distance of the collimator lens 2 changes due to a temperature change, the distance between the collimator lens 2 and the chip 1b of the semiconductor laser 1 changes by an amount substantially equal to the change in the working distance, resulting in collimation deviation. Will be compensated.

FIG. 6 is a diagram showing the holding member 5, the support 9 and the holding member 8 in FIG. 1 in a simplified manner. FIG. 6A shows a normal temperature state during adjustment, and FIG. 6B shows a high temperature state. Shows. As described above, since the holding member 5 and the holding member 8 have the same linear expansion coefficient, the amount of expansion / contraction when the temperature changes in the facing flange portions is equal, and the mounting position of the support 9 is the holding member 5 and the holding member. 8 does not shift in the direction orthogonal to the optical axis. Therefore, the positional relationship between the holding member 5 and the holding member 8, that is, the positional relationship between the semiconductor laser 1 and the collimator lens 2 is not broken by the temperature change, and the light from the semiconductor laser 1 is always accurate by the collimator lens 2. Is a parallel light flux.

Although the light source section of the optical head has been described in the above embodiment, the present invention is also applicable to the light receiving section. For example, an imaging lens (optical member) and P
In the signal detection unit including an IN photodiode (photoelectric conversion means), the collimator lens 2 in FIG. 1 may be replaced with an imaging lens, and the semiconductor laser 1 may be replaced with a photodiode. In this case, the positional relationship between the imaging lens and the photodiode is not destroyed by the temperature change, and the focus error due to the temperature change can be prevented.

[0029]

As described above, according to the present invention, the first holding means for holding the light emitting means or the photoelectric conversion means and the second holding means for holding the optical member have the same linear expansion coefficient. The mounting position of the support member interposed between the fastening portions of both members does not shift between the first holding member and the second holding member. Therefore, even if there is a temperature change, the positional relationship between both holding members is not broken, and deterioration of the optical characteristics of the light source unit or the light receiving unit due to the temperature change can be avoided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a light source unit including a temperature compensation structure according to an exemplary embodiment of the present invention.

FIG. 2 is a sectional view for explaining temperature compensation in the embodiment of the present invention.

FIG. 3 is a sectional view illustrating a light source unit having a conventional temperature compensation structure.

FIG. 4 is a cross-sectional view for explaining temperature compensation of a conventional light source unit.

5A and 5B are partial cross-sectional views for explaining problems in the light source unit of FIG. 4, FIG. 5A showing a state at room temperature and FIG. 5B showing a state at high temperature.

6A and 6B are views for explaining the operation in the embodiment of FIG. 1, in which FIG. 4A shows a state at room temperature and FIG. 4B shows a state at high temperature.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 1a ... Heat sink, 1b ... Semiconductor chip, 2 ... Collimator lens, 3,7,8 ... 1st holding member, 4, 6 ... Press ring, 5 ... 2nd holding member, 9 ... Support, 10 ... Screw, 11 ... Spring washer, 12 ... Device main body.

Claims (4)

[Claims] 1. A first holding member for holding a light emitting means or a photoelectric conversion means, and a second holding member for holding an optical member arranged in an optical path of a light flux emitted from the light emitting means or a light flux incident on the light receiving means. Holding member and a support member having a linear expansion coefficient different from that of the first holding member, the first and second holding members are fastened with the support member interposed therebetween, The length in the fastening direction is determined so as to compensate for the distance between the light emitting means or the photoelectric conversion means and the optical member with respect to temperature change, and the first and second holding members have the same linear expansion coefficient. A temperature compensating structure for a light source unit or a light receiving unit. 2. The temperature compensating mechanism, wherein at least one of the first and second holding members comprises a plurality of members having the same linear expansion coefficient. 3. The temperature compensating structure for a light source unit or a light receiving unit according to claim 1, wherein the light emitting means is a semiconductor laser. 4. The temperature compensating structure according to claim 1, wherein the photoelectric conversion means is a PIN photodiode.